This invention relates in general to distributor-type fuel injection pumps for compression ignition internal combustion engines or Diesel engines and more particularly to governors of such fuel injection pumps.
In FIG. 1, there is shown a prior art distributor-type fuel injection pump for a compression ignition multi-cylinder internal combustion engine.
The prior art distributor-type fuel injection pump comprises a pump housing 1 having an inner chamber 1a which is charged with fuel by a fuel supply pump (not shown). To the pump housing 1 there is fixedly attached a plunger barrel 2 in which is mounted a distributor plunger 3. The distributor plunger 3 is powered by engine-driven power transmitting means (not shown) and reciprocates while rotating to effect pumping and distributing actions.
During the suction stroke or leftward stroke of the distributor plunger 3, fuel is drawn from the inner chamber 1a through an inlet channel 4 and longitudinal grooves 5 provided in the outer face of a terminal portion of the distributor plunger 3 to a pump work chamber 6 which is adjoined by the distributor plunger 3. During the pressure stroke or rightward stroke of the distributor plunger 3, fuel under pressure is delivered from the pump work chamber 6 through a distributor channel 7 to one of outlet channels (only one is shown). Therefrom fuel is delivered through the associated one of delivery valves 9 to one of injection nozzles (not shown). In this manner, fuel is sequentially injected into the cylinders of the engine.
In the distributor plunger 3 there is provided a transverse channel or relief channel 10 which cooperates with a control sleeve 11. The control sleeve 11 is axially displaceable on the distributor plunger 3 to seal and unseal the mouths of the relief channel 10 in the outer surface of the distributor plunger 3. When the control sleeve 11 unseals or uncovers the mouths of the relief channel 10, the pump work chamber 6 is drained into the inner chamber 1a of the pump housing 1 to terminate the fuel delivery to the injection nozzles. Hence it is possible to alter the terminal moment of fuel delivery during each pressure stroke of the distributor plunger 3 and therefore the quantity of fuel delivered to the engine by changing the position of the control sleeve 11. For example, leftward displacement of the control sleeve 11 in the drawing results in reduced injected fuel quantity.
The axial position of the control sleeve 11 is controlled by a governor mechanism which comprises a governor shaft 12 which is fixedly attached to the pump housing 1. On the governor shaft 12 there is rotatably mounted a centrifugal weight holder 13. The holder 13 is powered by the aforementioned power transmitting means (not shown) for the distributor plunger 3 by way of a multiplying gear (also not shown). On the centrifugal weight holder 13, centrifugal weights 14 are supported and rotated about the governor shaft 12 and swing outwardly due to centrifugal force. As the weights swing outwardly, fingers 14a axially displace a governor sleeve 15on the governor shaft 12, in the rightward direction in the drawing. The governor sleeve 15 abuttingly engages at the left-hand end thereof with the upper arm portion of a starting lever 16 which is swingably supported on a pivot 17. The lower arm portion of the starting lever 16 has a spherical terminus 16a which extends into a depression of the control sleeve 11 for causing axial displacement of the control sleeve. On the pivot 17 there is also swingably supported a tensioning lever 18. Between the tensioning lever 18 and the starting lever 16 there is interposed a starting spring or an excess fuel spring 19 in the form of a leaf spring. The tensioning lever 18 is operatively connected through an idle spring 20, a governor main spring 21 and a control lever 22 to an accelerator pedal (not shown). Stopper 23 limits the extent of counter-clockwise swing of the tension lever 18.
The operation of the governor mechanism thus described will be explained hereinbelow with additional reference to FIG. 2.
When the engine is stopped and therefore the centrifugal weights 14 are motionless, the centrifugal weights 14 assume the completely closed condition due to the bias of the starting spring 19 transmitted thereto by way of the starting lever 16 and at the same time control sleeve 11 is moved into the starting position or the most rightward position thereof (represented by the horizontal line A in the graph of FIG. 2) in the drawing (FIG. 1) whereby an excess fuel quantity required by the engine during starting is obtained.
When the engine starts and in the absence of depression on the accelerator pedal, the control lever 22 is put into the idle position and therefore the tension of the governor spring 21 reduces approximately to zero. The centrifugal weights 14 are thus permitted to swing outwardly even in the relatively low rotational conditions thereof which displaces the governor sleeve 15 rightwardly turning the starting lever 16 together with the tension lever 18 and compressing both the starting spring 19 and the idle spring 20, resulting in the movement of the control sleeve 11 leftwardly into the idle position which is determined by the balance of the centrifugal force and the biasing forces of the starting spring 19 and the idle spring 20. In this manner, the quantity of fuel necessary for smooth idling of the engine is obtained as represented by the point B in the graph of FIG. 2.
When the accelerator pedal is then depressed to move the control lever 22 to some extent, the tension of the governor main spring 21 becomes larger and consequently both the starting spring 19 and the idle spring 20 are compressed to be of shorter length permitting the tension lever 18 to swing counterclockwise until it abuttingly engages the stopper 23. Actuated by such swing of the tension lever 18, the starting lever 16 displaces the control sleeve 11 to the full load position as is represented by the point C in the graph of FIG. 2. The control sleeve 11 remains thereat permitting the engine speed to increase up to the value as is represented by the point D in the graph of FIG. 2 where the centrifugal weights 14 start to displace the governor sleeve 15 overcoming the counter force thereto. After that, the control sleeve 11 is displaced in the fuel-increasing direction, i.e., leftwardly to the position as represented by the point E in the graph of FIG. 2 which is determined by the balance of the centrifugal force of the centrifugal weights 14 and the biasing forces of the springs 19, 20 and 21. The engine speed is thus controlled with relation to the amount of depression on the accelerator pedal.
The pivot 17 is carried on a full load fuel quantity adjusting lever 24 which is pivotally supported on a stationary pivot 25. The adjusting lever 24 is normally held stationary but is caused to swing about the stationary pivot 25 by rotating a screw 26 to change the setting of the full load fuel quantity. A fuel-cut solenoid valve 27 is provided for stopping the engine.
The governor sleeve 15 has an inner space 30 which is adjoined by an end of the governor shaft 12 and which varies in volume in response axial displacement of the governor sleeve on the governor shaft. In order to draw fuel from the inner chamber 1a of the pump housing 1 into the inner space 30 and on the other hand to discharge fuel from the inner space 30 into the inner chamber 1a in response to the variation in volume of the inner space 30, there is provided in the governor sleeve 15 an opening P which provides communication between the inner space 30 and the inner chamber 1a. The flow passage sectional area of the opening P has heretofore been designated to be relatively large for the reason of good responsiveness.
Though the prior art distributor-type fuel injection pump with such a governor mechanism produces good results upon engine deceleration due to the good responsiveness, it tends to produce undesirable results upon rapid engine acceleration due to the good responsiveness. That is, upon rapid engine acceleration, the control lever 22 actuates, by means of the governor main spring 21, the starting lever 16 toether with the tension lever 18 to rapidly swing in the counterclockwise direction displacing the governor sleeve 15 leftwardly in the drawing. In response to such displacement of the governor sleeve 15, the control sleeve 11 is rapidly displaced rightwardly or in the fuel-increasing direction. As a result, the quantity of fuel delivered to the engine increases rapidly, resulting in an acceleration jerk which prevents good drivability and causes a smoky exhaust emission from the engine. This occurs because, at the initial stage of the rapid engine acceleration, the rate of engine air flow can not quickly increase so as to match the increased quantity of fuel delivered to the engine, that is, the increase in the rate of engine air flow lags behind the increase in the quantity of fuel delivered to the engine.